Authigenic Preservation
From Talk:Taphonomy
A form of plant preservation, also known as cementation, that involves casting and molding. Iron or carbonate minerals become cemented around the plant, and with time the actual plants dissolves away. The cemented minerals produce a cast of the external and internal faces of the plant. The void left by the plant might later be filled with sediment producing a mold of the plant.
Aelennartz (talk)